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Depression is one of the leading causes of disability in older adults worldwide. Many older adults with depression are undetected, and there is a need for brief, scalable psychological treatments for depression that can be delivered remotely.

The aims of this thesis were 1) to investigate the diagnostic accuracy of two rating scales (PHQ-9 and GDS-15) for the detection of depression in older adults, and 2) to investigate the feasibility, preliminary efficacy and patients’ experiences of a telephone-based psychological intervention, Behavioral activation with mental imagery (BA-MI), for the treatment of depression in older adults in the context of the covid-19 pandemic. 

Study I showed that a cutoff of ≥6 on the GDS-15 and ≥5 on the PHQ-9 were optimal to identify major depressive disorder. When identifying both major depressive disorder and subthreshold depression, the optimal cutoff on the GDS-15 was ≥5. Study II was a randomized clinical pilot trial, CoviDep, with a treatment group receiving the BA-MI intervention, and a control group. The drop-out rate was low. Compared to the control group, the treatment group reported a decrease in depressive symptoms throughout the treatment, with a large effect-size at posttreatment. Study III was a long-term follow-up of participants in CoviDep that received the BA-MI intervention. The drop-out rate over time was low, and compared to baseline, decreases in depressive symptoms were observed with a medium effect-size at posttreatment that was maintained 1- and 3 months post-treatment but lower after 6 months. Study IV was a qualitative study. The BA-MI intervention in CoviDep was described as increasing activities and improving mood. Telephone-delivery reduced barriers due to pandemic restrictions but felt less personal and lacking non-verbal communication. Being recognized and talking to a therapist every week was healing, but the manualized mode of treatment seemed to impair the relationship.

In sum, this thesis shows that both the GDS-15 and the PHQ-9 are useful tools for the detection of depression in older adults, and adds to the support for telephone-delivered BA for the treatment of depression and indicates that MI-interventions are feasible as an augmentation of BA in older adults.